1. Field of the invention
The present invention relates generally to an antenna for a mobile communication terminal, and more particularly to a Printed Circuit Board (PCB) contained in a case and an embedded antenna for a mobile communication terminal having double feed points using the same.
2. Description of the Prior Art
As generally known in the art, current mobile communication terminals are expected to provide more services, in addition to satisfying requests for compactness and lightness. In order to satisfy such requests, internal circuits and components for mobile communication terminals are becoming smaller while incorporating more functions. Such a trend is no exception in the case of antennas, which are one of the major components of mobile communication terminals.
Considering this, it has been proposed to install antennas inside the case of mobile communication terminals (i.e. embedded antennas).
FIG. 1 is an exploded perspective view of an embedded antenna 100 for a mobile communication terminal, which has a single feed point 33, according to the prior art. FIG. 2 is a perspective view of the embedded antenna 100 shown in FIG. 1. Referring to FIGS. 1 and 2, the conventional embedded antenna 100 includes a case 10, a PCB 20 contained in the case 10, and an emission carrier 30 formed in a planar shape at a predetermined distance from the upper surface of the PCB 20.
The emission carrier 30 includes a dielectric plate 31 and an emission wiring layer 32 formed on a surface of the dielectric plate 31. The emission wiring layer 32 includes a feed point 33 and a ground point 35 formed on the lower surface of the dielectric plate 31 while being adjacent to each other, an emission pattern 36 formed on the upper surface of the dielectric plate 31, and a connection pattern 38 connecting the feed and ground points 33 and 35 to the emission pattern 36, respectively. The emission pattern 36 has a U-slot 37 formed therein so as to implement a dual band.
The PCB 20 includes an insulative body 21 and a feed wiring layer 22 formed on the body 21. The feed wiring layer 22 includes a ground layer 23 formed on the lower surface 21a of the body 21, as well as a feed pad 24 and a ground pad 27 formed on the upper surface 21b of the body 21. The ground pad 27 is connected to the ground layer 23. The feed and ground points 33 and 35 are connected to the feed and ground pads 24 and 27 via connection tips 28, respectively.
When a current is supplied to the feed point 33 connected to the feed pad 24 of the conventional embedded antenna 100, it flows through the connection pattern 38 and the emission pattern 36 so that electromagnetic waves in a dual frequency band are emitted.
However, the conventional embedded antenna 100 has a limitation in that, since a single feed point 33 emits electromagnetic waves via a two-dimensional emission pattern 36, the frequency bandwidth of emitted electromagnetic waves is narrow, as shown in FIG. 3. This is an obstacle to expanding the frequency bandwidth. Particularly, the conventional embedded antenna 100 has narrowband characteristics in the low-frequency band, i.e. 837-903 MHz (7.06%) at a bandwidth of −10 dB.
Considering that users commonly grasp the case 40 of their mobile communication terminals by hand and place it on their ear during use, a frequency shift may be caused by the influence of human bodies, as shown in FIG. 4. The frequency shift may result in deviation from the narrow frequency bandwidth of the conventional embedded antenna 100. In this case, the embedded antennas 100 may deteriorate and fail to function properly. More particularly, in the case of the conventional embedded antenna 100, spots “1” and “2” belong to a Code Division Multiple Access (CDMA) band of 824-894 MHz. The resonance spots may shift towards the low-frequency region under the influence of human bodies and eventually deviate from the CDMA band.